WHEN William Joppy climbs into the ring against Bernard Hopkins Saturday night in Atlantic City, his motivation is not only to win the undisputed middleweight championship but also win a fight he has dedicated to his baby daughter, who was only six weeks old when she died last July.

“This fight is for her,” Joppy said in a telephone interview yesterday. “It still hurts real bad. But life goes on. There’s a reason for everything. God doesn’t make mistakes.”

The circumstances surrounding Vashti Joppy’s death aren’t totally clear. Joppy, 33, and his girlfriend welcomed her birth on May 29. The couple wasn’t living together and all Joppy knows is that while someone was babysitting his daughter in mid-July, the baby was dropped and landed on her head, causing severe brain damage.

She remained in a coma, clinging to life in critical condition for about a week before passing away in a hospital near Joppy’s home just outside Washington D.C. There are reports the babysitter, a grown woman, had left the child with teen-agers when the tragedy occurred.

Five months later, Joppy will enter the ring for the biggest fight of his career, his fallen daughter serving as inspiration. “My baby is going to be right there with me,” Joppy said. “She’ll be right there.”

Those closest to Joppy, who has three other children, said he’s ready mentally and physically to get back in the ring.

“He seems to be in a pretty good frame of mind,” said William Joppy Sr., who helped his son get through the ordeal. “I’m sure he thinks about what happened. But not to the extent that it would damage him for this fight. I think he’s more motivated for this fight than any other fight. I think he sees this fight as his justice.”

Joppy (34-2-1, 25 KOs) owns the WBA middleweight title vacated by Hopkins following his destruction of Felix Trinidad at the Garden in 2001. In that same tournament, Joppy was overwhelmed by Trinidad in the semifinals, being knocked down in three different rounds before losing by TKO in the fifth. He has since won his last two fights, beating Howard Eastman to win the WBA belt again and then successfully defending against Naotaka Hozumi in Tokyo 13 months ago. But it’s Hopkins who remains the recognized king of the division.

While this is the 14th world title fight for Joppy, Hopkins (42-2-1, 31 KOs) is defending a middleweight title for the 17th time. Their bout if one of five championship fights on the pay-per-view card at Boardwalk Hall.

Joppy’s manager, Steve Nelson, has watched his fighter go from heartbroken father to focused fighter.

“He actually took things the hardest when she was clinging to life in the hospital,” Nelson said. “Once they had the funeral, it was like closure for him. At that point, all that was in his mind is that the Hopkins fight was coming up. He’s over the death. He has closure. Now he’s as motivated and focused as I’ve ever seen him in four years.”